Discussion Session: FAMOS, Oct. 2013 Major Challenges for biogeochemical modelling and observations: what is needed to improve both observing systems and models including coordinated experiments

P N D Z Diagnostic variables Validation Rates/Fluxes Spatially and temporally averaged quantities incl. variance and uncertainty P D Z N Chl Rates/Fluxes Diagnostic variables Validation Regional model studies Localized Process model studies (Parameterisation development) Climate model studies Site specific quantities from field and Lab experiments (duplicates) Spatially averaged quantities incl. spatial variability Conceptual models Complexities and interactions Community structure Plankton Functional Types Multi nutrient Types of measurements Types of model studies Types of model data Prognostic variables

Model needs and abilities Main limitation for model development is validation => need observational data => ideal dataset varies with the model: data sets covering all seasons and most of the model domain and be available as a gridded dataset, data- rich (large range of quantities) long timeseries at a specific location or data rich short process studies with high temporal resolution. Modellers can create dynamics of bgc processes, but don't have the information to constrain the parameters (quantification) => models have to remain simpler Issues: Model scale versus sampling scale/Consistency in definitions of quantities (in models and obs) Sensitivity studies Feedback to observationalists => guide studies

Observations Consistent methods and reporting (e.g. Miller et al. - BEPSII for sea-ice bgc) Need for information on instrument precision Need for redundant observations to independently validate observational datasets Need for duplicate/triplicate measurements => information on standard deviation and variance => uncertainty ranges for model sensitivity studies

Main physical drivers: 1. Sea Ice cover, 2 Main physical drivers: 1. Sea Ice cover, 2. snow melt/melt ponds/brine release – subgrid scale representation, 3. stratification/mixing/tides, 4. upstream properties - water Inflow What coordinated experiments are needed? - possible??? Process oriented studies: Light transfer through sea-ice (Light versus nutrient limitation) Near surface mixing => stratification Deep Chlorophyll Maximum: seasonality/duration/magnitude/depth Other: Recommendation for CMIP6 ?